The invention concerns a method for the constant maintenance of the mean gap width between a sonotrode of an ultrasonic system and a tool of an ultrasonic cuffing device, designed as a counter surface, for cuffing and/or welding of various types of materials such as, for example, synthetic foils, textile fabrics containing synthetic substances, with the use of an adjusting device, wherein the contacting time between the sonotrode and a contacting surface for maintaining a constant clearance between the sontrode and at least one counter surface is kept constant by way of a control system.
In order to generate ultrasound and to apply it to a medium with a certain required performance rating, an ultrasonic transducer (xcex/2-generator), which converts the applied electric energy into mechanical vibrations, a sonotrode and/or a horn are used in principle.
The sonotrode is to be regarded as a tool by way of which the ultrasonic power is conducted to the location of effect.
According to the general state of the art, the material course or the material courses placed over each other are conducted between a counter tool, for example a cutting tool, and the ultrasonic unit.
The longitudinal vibrations transmitted into the material cause a heating-up and/or a splitting of the material and, subsequently, the welding and/or cutting action.
In order to achieve a constant and optimal welding and cutting quality as well as achieving a minimisation of the cutting tool wear, the setting of an optimal and constant mean welding and/or cutting gap width between the sonotrode and the tool is of particular significance.
In the DE 44 39 284 A1 a device for the continuous ultrasonic processing of a material course is described where the gap between the sonotrode and the counter tool is adjustable. The ultrasonic transducer unit is rigidly connected with the machine column by way of a temperature-controlled adjusting device. By means of the temperature-controlled adjusting device, temperature-related length changes in the ultrasonic speed are to be compensated so that the weld and cutting gap indicates a constant size.
The disadvantage here is that only the temperature-related length changes are registered and compensated, but not the length changes of the associated components which result from material elasticity and tool wear and which can amount to some xcexcm after, for example, the pass-through of a material course.
Therefore, the invention is based on the task assignment of developing a category-related method for the constant maintenance of the mean gap width of an ultrasonic cutting device, with which the drawbacks of the known methods and devices are avoided and with which it is ensured that different material types, particularly synthetic foils, can be welded and/or cut reliably and effectively at constant quality by means of the control of a constant and defined optimal gap width which is independent of external influential factors.
According to the invention, this task assignment is solved by the features of the independent claims. Correspondingly, the contacting time between the sonotrode and a contact surface for constant maintenance of the clearance between the sonotrode and at least one counter surface is kept constant by way of a control system. The control system consists, according to a most preferred embodiment follows, of two control circuits which are linked together. With a first and quick control circuit, using electronic means, the amplitude of the vibratory system (ultrasonic system) is continuously corrected and, subsequently, the contacting time is kept constant at quick cyclic load. With a second and slower control circuit, whose control time however is faster than the temperature change in the system, and with the assistance of at least one actuating element, thermally related and wear-related clearance changes which can no longer be compensated by the amplitude control because of their expected size, are compensated between the cutting tool and the sonotrode so that the pre-set contacting time is kept constant.
In this way, the real clearance and the real gap width, respectively, are covered. Deviations from the setpoint are automatically compensated independent of the influential factors. Constantly good and reproducible welding and cutting results as well as a minimum wear of the cutting tool and the sonotrode are ensured.
According to an embodiment of the invention, and by means of a suitable lever mechanism, two or several mean gap widths are kept constant, even then, when for example, re-regulation is necessary following wearing of a cutting point. The gap width of the following stage is individually smaller or equally as large as the gap width of the previous stage. In this way, for example, welding and cutting with a wear compensation during cutting is ensured. The welding and cutting geometries are independent of each other. For this reason, for example, it is possible to weld on a broad scale and to cut with an acute angle.
With separated and two-stage welding and cutting, respectively, the processing speeds increase considerably without reduction of the edge quality because, during the welding process, more energy can be applied to the material as the material has not yet been separated during the first treatment process.
The applied tools can be arranged and used in a variety of ways. For example, the non-contacting tool can be trunnion-mounted and can have a profiled surface.
Tool arrangement can also be such that one tool is vibratory and one tool is stationary in its position.
Advantageous embodiments of the invention according to independent claims result from the further Subclaims.